1. Field of the Invention
This invention relates to an improved design for an applicator tip, particularly for use with an applicator that dispenses adhesive material. In particular, the present invention relates to an applicator tip that exhibits an improved flow pattern of the adhesive material in the applicator tip, which allows for more precise placement of the adhesive material and decreased waste of adhesive material.
2. Description of Related Art
Monomer and polymer adhesives are used in both industrial (including household) and medical applications. Included among these adhesives are the 1,1-disubstituted ethylene monomers and polymers, such as the xcex1-cyanoacrylates. Since the discovery of the adhesive properties of such monomers and polymers, they have found wide use due to the speed with which they cure, the strength of the resulting bond formed, and their relative ease of use. These characteristics have made the xcex1-cyanoacrylate adhesives the primary choice for numerous applications such as bonding plastics, rubbers, glass, metals, wood, and, more recently, biological tissues.
It is known that monomeric forms of xcex1-cyanoacrylates are extremely reactive, polymerizing rapidly in the presence of even minute amounts of an initiator, including moisture present in the air or on moist surfaces such as animal (including human) tissue. Monomers of xcex1-cyanoacrylates are anionically polymerizable or free radical polymerizable, or polymerizable by zwitterions or ion pairs to form polymers. Once polymerization has been initiated, the cure rate can be very rapid.
Medical applications of adhesive compositions include use as an alternate or an adjunct to surgical sutures and staples in wound closure as well as for covering and protecting surface wounds such as lacerations, abrasions, burns, ulcers such as stomatitis, sores, and other open surface wounds. When an adhesive is applied to surfaces to be joined, it is usually applied in its monomeric form, and the resultant polymerization gives rise to the desired adhesive bond.
However, with the application of adhesive in its monomeric form, due to the rapid polymerization rate of the monomers, it has been challenging to design effective and commercially viable packaging and dispensing systems. Such packaging and dispensing systems must counterbalance the competing requirements that the monomer not prematurely polymerize, that the monomer be easily applied, that the monomer polymerize at a desired rate upon application, and that the sanitary and/or sterile properties of the monomer and applicatorxe2x80x94whether real or perceivedxe2x80x94be maintained.
In order to meet the above requirements, various dispensing and packaging systems for adhesives have been proposed. These systems include large bottles with a single applicator, such as a large single- or multi-use brush; small applicators such as small ampoules containing monomer, for example within an internal frangible vial, that can be expelled through an integral or replaceable applicator; and the like. However, a problem with many of these applicator systems is that the product contains more adhesive material than is necessary for a particular use. Because of the rapid polymerization rate of the monomers, any unused adhesive is generally discarded, because either the remaining monomer undergoes polymerization, or the monomer polymerizes within the applicator to render the applicator unusable.
A disadvantage of some known applicator systems, and particularly applicators containing a frangible vial and a porous applicator tip for expelling the adhesive, is that monomer material may be wasted by filling the pores of the applicator tip in areas other than the areas used to apply the adhesive. Furthermore, some known applicator tips suffer from the problem of the monomer being expelled through the entire surface area of the tip, and even to greater extents in areas other than the area used to apply the monomer to the desired substrate. For example, large amounts of adhesive become expelled from areas around the periphery of the applicator tip, where the applicator tip meets the applicator housing, rather than through the end of the applicator tip, as is often desired. This leads to a further problem of less precise control over the area of application of the monomer to the substrate.
For example, an effective applicator system is disclosed in U.S. Pat. No. 5,928,611 to Leung. This patent discloses an applicator system generally comprising a tube containing a frangible vial of monomeric adhesive composition. One end of the tube is sealed, and the other end is closed by an applicator tip comprising a solid support having a polymerization or cross-linking accelerator or initiator for the monomeric adhesive disposed thereon or therein. As shown in FIG. 3 of the patent, the applicator tip can be generally dome shaped. An applicator device of U.S. Pat. No. 5,928,611 is shown as FIG. 1 herein. The applicator device 100 comprises a cylindrical applicator container 200 holding polymerizable and/or cross-linkable material 300 enclosed in a frangible vial 400, and an applicator tip 500 containing a polymerization and/or cross-linking initiator.
However, a difficulty encountered with such a dome-shaped applicator tip, as well as with other solid applicator tips, is that the monomeric adhesive material being expelled through the applicator tip tends to follow paths of least resistance within the tip. That is, as the monomeric adhesive is being expelled, it tends to follow the shortest paths through the tip, which tend to be around the periphery of the tip, rather than following the longer path through the full length of the tip to the end of the tip. Because the end of the tip is desired to be used to apply the adhesive, less precise control of placement of the adhesive is obtained because adhesive becomes expelled through the entire surface of the tip. This also tends to result in waste of adhesive material, because all of the adhesive does not exit from the tip at the same location.
Applicator devices commercially used for Loctite Product No. 11067-2 and Permatex Product No. ATA-1 contain crushable glass ampoules within flexible applicators. However, the compositions within the crushable ampoules are, in both products, adhesive activators, not the adhesive composition itself. In both of these products, the adhesive is contained in a separate dispenser. The dispenser system used for these products is physically similar to that shown in FIG. 1, except that the applicator tip is rectangular in shape, rather than dome-shaped, and the applicator tip does not contain a polymerization and/or cross-linking initiator for an adhesive material contained in the frangible vial. In this product also, the above-described problems of wasted material (here, initiator) and less precision in application are also present.
Accordingly, a need exists in the art for improved applicator tip designs, which will allow more precise placement of the adhesive material. A need also exists in the art for a means to decrease waste of monomeric adhesive material, by ensuring that the adhesive material either exits at the desired location of the applicator tip, or flows to such a desired location on the tip.
The present invention addresses the above needs by providing applicator tips that possess increased precision in control of placement of the adhesive composition, and a decrease in waste of adhesive. The applicator tips of the present invention provide either more uniform or preferentially controlled paths of resistance within the applicator tip, or provide means for channeling adhesive to an application zone and away from other surface areas of the applicator tip.
A benefit provided by the present invention is thus the ability to apply adhesive material in precise patterns, such as in thin lines. The present invention also allows tailoring of the application pattern based on alternative designs of the applicator tip, thus allowing flexibility in application of, for example, from thin lines to thicker lines. The present invention also decreases waste of adhesive material, by allowing effective use of a greater portion of the volume of adhesive material contained within the applicator. In embodiments, it also improves the utilization of polymerization and/or cross-linking initiator and/or rate modifiers present in the tip.
The present invention provides an article of manufacture for dispensing adhesive material, comprising a container body, and a porous applicator tip having a proximal end that is inserted into or attached to the container body, and a distal end located away from the container body, wherein the adhesive material is located in the container body in a non-contacting relationship with the applicator tip prior to dispensing the adhesive material.
In embodiments of the present invention, a flow path length ratio A/B is less than 1.5, wherein B represents a length of a shortest flow path of adhesive material through the material of the applicator tip to an external surface of the applicator tip adjacent the container body, and A represents a length of a shortest flow path of the adhesive material through the material of the applicator tip to an external surface of a predetermined application subportion such as the distal end of the applicator tip. In embodiments, the applicator tip comprises one or more grooves that channel adhesive exiting the applicator tip from peripheral portions of the applicator tip to the distal end of the applicator tip. In embodiments, the applicator comprises a protective cover surrounding at least a part but not all of an area of the applicator tip extending out of the container body. In embodiments, the applicator tip is a hollow porous applicator tip having a proximal end that is inserted into or attached to the container body, and a distal end located away from the container body.